IOD Haemolytic Anaemia Flashcards
(30 cards)
What is haemolytic anaemia?
Increased peripheral destruction of RBCs
Shortened RBC life span (normally 120 days)
Bone marrow continues to produce cells
Pathology is in the red cell itself, or it’s environment
Increased consumption means BM has to work harder to compensate.
As the BM tries to keep up, the patient becomes anaemic
RBC destroyed > RBC produced
Categories of haemolysis?
Inherited-present from birth Immune-Antibody mediated Extravascular-site of destruction is the spleen and other RES organs Acquired-Develops de novo Non-immune-RBC or environment Intravascular-site of destruction is within the vascular space
Inherited non-immune types?
Sickle cell disease-extravascular & intravascular
Membrane disorders-eg Hereditary Spherocytosis extravascular
G6PD deficiency -
intravascular
acquired non immune problem with RBC?
Paroxysmal Nocturnal Haemoglobinuria (PNH)
intravascular
acquired non immune problem with RBC environment?
Microangiopathic haemolysis (MAHA): TTP, DIC, HELLP intravascular Valve haemolysis intravascular
Acquired Immune AB-mediated attack on RBC’s?
Autoimmune: warm, cold, drug induced
intravascular & extravascular
Alloimmune – transfusion reactions, HDFN intravascular
Investigations?
Haemolysis Screen
FBC: Normocytic anaemia
Blood film: Spherocytes or red cell fragments
Reticulocytes: Increased
LDH: Increased (due to cell turnover)
Bilirubin (on RBC membranes):Increased (unconjugated)
Haptoglobin (binds to free Hb in plasma to remove it):Decreased in intravascular haemolysis
DAT: Positive in some immune cases
Intravascular results?
↑ unconjugated bilirubin ↑ LDH ↑ Reticulocytes ↓ haptoglobin Haemoglobinuria Haemoglobinaemia Haemosiderinuria
extravascular
↑ unconjugated bilirubin ↑ LDH ↑ Reticulocytes normal haptoglobin No Haemoglobinuria No Haemoglobinaemia No Haemosiderinuria
Acquired immune haemolytic anaemia types?
Auto-immune-self as foreign Warm AIHA Cold AIHA Cold Haemagglutinin Disease (CHAD) Paroxysmal Cold Haemoglobinuria (PCH) Drug induced
Allo-immune-foreign as foreign Transfusion reactions Haemolytic Disease of Fetus and Newborn (HDFN)
Autoimmune Haemolytic Anaemia?
Autoantibodies directed against a patients own RBC’s
Usually IgG (generally warm AIHA)
or
IgM (generally cold AIHA) mediated
Warm and Cold classifications due to the behaviour of the antibodies involved and whether they react more strongly with RBC’s
at 370C or 40C
May have a mixed picture in reality
DAT?
Blood sample form a pt has ABs on RBC surface
Washed RBCs incubated with antihuman antibodies
RBC’s agglutinate-antihuman antibodies form links by binding to antibodies on RBC’s
Warm AIHA?
Usually IgG mediated: DAT +ve: AutoAb binds to RBCs at 37 degrees, Removed by RE macrophages Part of RBC membrane lost: spherocyte Destroyed in the spleen prematurely Extravascular
50% idiopathic
Other associations – CLL-leukaemia, LPD-lymphoma, SLE-lupus, RA
Cold AIHA?
Usually IgM mediated: Complement + DAT
Primary CHAD
Ab binds to RBCs at 40C, causes red cell agglutination on blood film, worse in the cold (transport sample in the warm)
Associated with acrocyanosis, Raynauds, intravascular haemolysis.
Often triggered by Mycoplasma pneumonia, EBV (Secondary CHAD)
May be associated with underlying LPDs.
Paroxysmal cold haemoglobinuria?
Paroxysmal cold haemoglobinuria (PCH)
Donath-Landsteiner antibody – biphasic. Binds to RBCs at 370C and lyses them at 200C. Often triggered by viral infections.
(in exams tends to be a child playing outside, who comes in to a warm house…!)
management AIHA?
Look for associated/ underlying conditions and treat WARM Steroids, blood as needed Rituximab (anti-CD20), splenectomy COLD Keep warm, blood warmers Occasionally chemotherapy if LPD
Acquired Non-IMMUNE?
MAHA: Microangiopathic haemolytic anaemia
Characterised by mechanical destruction (due to environment) of red blood cells and therefore fragments (schistocytes) on the blood film
Often associated thrombocytopenia
(Thrombotic Microangiopathy)
Predominantly an acquired intravascular haemolysis
Thrombotic Thrombocytopenic purpura?
Rare
Text book – pentad:
1. Fever 2. Renal failure 3. Confusion
4. Thrombocytopenia 5. MAHA on blood film
Low plts, low Hb, high bili, high LDH, high creat, +/-positive troponin
Microthrombi
Often idiopathic, but also due to:
HIV, pregnancy, drugs, congenital
Diagnosis and management?
Endothelial cell damage releases ultra large vWF multimers into the bloodstream which bind to vWF receptors on platelets, causing aggregation.
Reduction of ADAMTS 13 (normally proteolyses vWF multimers)
with associated IgG antibody against ADAMTS 13
ADAMTS 13 is vWF cleaving protease
Reduction leads to platelet aggregation and so cleaving of RBCs
No antibody in congenital forms: VERY RARE
Treatment
Plasma exchange, high-dose steroids, blood, folic acid
Rituximab, RRT?
Aspirin and prophylactic LMWH when platelets recover
Hb structure?
2 alpha chains & 2 beta chains Producing HbA (>90%) and some HbA2 (<5%)
SCA?
Caused by an abnormality in globin chain structure
They are caused by single gene disorders
The most common are the ‘Sickle Cell Diseases’
There are others such as congential dyserythropoietic anaemia (CDA)
Thalassaemias?
The thalassaemias are caused by absent or reduced production of the alpha or beta globin chains which form the normal adult haemoglobin HbA (⍺2β2).
Caused by mutations in regulatory genes
Might overlap with haemoglobinopathies: HbS/beta thalassaemia
genetics of SCC?
Point mutation in the beta globin gene on chromosome 11
Amino acid substitution (Adenine to thymine)
Causes glutamic acid being substituted by valine at position 6.
Diagnosis of SCA?
gel electrophoresis
sickle solubility
high performance liquid chromatography
